2008 z71 flashing cell

OK about a month ago my cel was flashing and my truck ran rough toomey it to the dealer he said I had a misfire on #7 and#1 cylinders did a tune up and also changed.the valve cover on the driver side it was recommended by the dealership so I did (I did all the work myself ) Now my truck is doing the same thing so I pulled the plugs to see if any were fouled out and nope all looked good haven't got the computer read for the codes yet seeing I work nights I am gonna have it done over the weekend dies any one have any suggestions on what to do?

Yes you can switch coils around to see if the codes reflect the
change, if they do then you have bad coils and or cables. If not then
you have to go deeper possible injector problems. I would dump a
bottle of Techron in the tank, and run it a few days then clear the
codes and see if they return.

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